A configuration is known in which an air belt passes through a shoulder portion of a seat back, wherein an air belt guide that is erected at a seat width direction outer side with respect to the expanded air belt is provided at the shoulder portion of the seat back. (For example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2007-112415. Further, with respect to an air belt device, refer to the specification of United States Patent Application Publication No. 2003/0168837 and Japanese National Phase Publication No. 2001-521462.)